1. Field of the Invention
The present invention relates to a dual fuel nozzle of a gas turbine combustor with a variable jetting hole diameter, and more particularly to a dual fuel nozzle of a gas turbine combustor with a variable jetting hole diameter capable of enhancing fuel flexibility in a multiple fuel system for applying two or more fuels to a gas turbine at the same time.
2. Description of the Related Art
Recently, development of various clean fuels has been conducted in many research institutions of the world to solve an emission problem of an energy source and an environmental problem. Many fuels such as biomass, a coal gas, GTL (Gas To Liquid Fuel) and CTL (Coal To Liquid Fuel) have been developed and commercialized recently. Also, the research and development have been conducted in a consumption field with the manufacture of the fuels.
A dry low NOx gas turbine employs a lean premixed combustion method, wherein a local high-temperature region in the diffusive flame is not generated, thereby suppressing the production of thermal NOx.
However, in the lean premixed combustion method, a mass ratio of a fuel amount to an air amount is 10% or less. It means that the control of the fuel amount is very important. Further, it is very difficult to reach stable combustion conditions of the lean premixed flame. Accordingly, combustion instability, combustion vibration, a backfire of the flame and the like are generated according to a mixing state of fuel and air and load conditions. Thus, there are problems such as damage of gas turbine parts due to abnormal combustion and large pressure variation or heat loss of parts and life reduction due to high-temperature flow (hot gas), thereby causing an increase in the maintenance and repair costs of a gas turbine.
Further, conventionally, when the gas turbine is operated at a low load, a noxious gas such as yellow plume caused by NO2 is discharged according to a combustion state. Thus, it may incur the enmity of the people around a power plant.
Recently, in the power plant using the gas turbine, a natural gas in which methane (CH4) has a volume ratio of 85% or more or distillate oil serving as a back-up fuel is used as a fuel. However, the fuel has a large range of fluctuation in market prices and a gas turbine capable of applying various power generation fuels thereto should be developed to correspond to the fluctuation range. Particularly, in the future, DME (dimethyl ether, CH3OCH3) which is a new fuel manufactured through a chemical processing method from various fuels such as a natural gas, coal, biomass and the like is expected to be applied after evaluating economical efficiency and technical efficiency. The DME has combustion characteristics such as a high burning velocity and a low ignition temperature. When the fuel is applied to the gas turbine power plant, the combustor may be burnt out due to the backfire of the flame. Also, a low heating value of the DME, 28.8 MJ/kg (59.3 MJ/Nm3), is lower than a low heating value of a natural gas, which is 49.0 MJ/kg (35.9 MJ/Nm3). Accordingly, it requires retrofitting of the combustor. Further, the combustor should be retrofitted to selectively use the natural gas and the DME fuel.
A dual fuel type gas turbine using heavy oil and natural gas, which is recently used for power generation, has independent channels which jet the fuel through different fuel jetting holes.
However, in the case of heavy oil power generation, the power generation cost is expensive and a noxious exhaust gas is largely generated. Accordingly, it is excluded from priority of power generation and the power generation is performed mainly using a natural gas as a fuel.